Simplified gate stack process to improve dual channel cmos performance

ABSTRACT

A semiconductor device and method of making the same wherein the semiconductor device includes a pFET region including a SiGe channel having a Si-rich top surface within the gate portion, and an nFET region including a Si channel. The method includes subjecting both the pFET and nFET regions to a single high-temperature anneal process thereby avoiding the need for an additional spike anneal process at RMG module.

DOMESTIC PRIORITY

This application is a Continuation of Non-Provisional application Ser.No. 15/603,982, filed May 24, 2017, which is a Divisional ofNon-Provisional application Ser. No. 15/275,565, filed Sep. 26, 2016,now U.S. Pat. No. 9,741,822; which are incorporated herein by referencein its entirety.

BACKGROUND

The present invention relates to integrated circuit chips, and morespecifically, to a design structure for upside-down field effecttransistors.

Integrated circuits (ICs) are implemented using a plurality ofinterconnected field effect transistors (FETs), which can be realized asmetal oxide semiconductor field effect transistors (MOSFETs or MOStransistors). The MOS transistor can include both a p-type device and ann-type device, wherein such a device is commonly referred to as acomplimentary MOS or CMOS device. A MOS transistor includes a gateelectrode as a control electrode that is formed over a semiconductorlayer having spaced-apart source and drain regions formed therein.Because of the higher density per unit area of microelectronic deviceson a chip, it is a challenge to reduce the parasitic or unwantedcapacitance between the gate conductor line and the metal filled viasthat form the contacts to the device source and drain.

SUMMARY

According to one embodiment, a semiconductor device is provided. Thesemiconductor device includes a pFET region including a first set ofspacers extending from the top surface of the SiGe channel, whereinbetween the first set of spacers defines a first gate, and a Si-richsurface on a portion of the top surface of the SiGe channel between thefirst set of spacers, wherein the first gate includes a first high-kdielectric layer in contact with the spacers, and a first metal gatematerial in contact with the high-k dielectric layer; and an nFET regionincluding a Si channel, and a second set of spacers extending from thetop surface of the Si channel, wherein between the second set of spacersdefines a second gate, wherein the second gate includes a high-kdielectric layer in contact with the second set of spacers, and a secondmetal gate material in contact with the second high-k dielectric layer.

According to one embodiment, a method of forming a semiconductor deviceis provided. The method includes providing a pFET region including aSiGe channel, a first set of spacers extending from the top surface ofthe SiGe channel, and a first dummy oxide including SiGeOx, wherein thefirst dummy oxide layer is positioned between the first set of spacers;providing an nFET region including a Si channel, a second set of spacersextending from the top surface of the Si channel, and a second dummyoxide layer including SiOx, wherein the second dummy oxide layer ispositioned between the second set of spacers; annealing the pFET and thenFET region to yield a Si— rich layer on a top surface of the SiGechannel; removing the first dummy oxide layer and the second dummy oxidelayer; depositing a first gate material between the first set of spacersand a second gate material between the second set of spacers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of CET versus spike anneal temperature at RMG for aconventional Si nFET.

FIG. 2 is a graph of Toxgl versus spike anneal temperature at RMG for aconventional Si nFET.

FIG. 3 illustrates a conventional SiGe gate stack.

FIG. 4 is a graph illustrating the D_(it) versus spike annealtemperature at RMG of the SiGe gate stack illustrated in FIG. 3.

FIGS. 5A-5B illustrates a conventional a-Si residue after spike annealin a nanosheet.

FIG. 6 is a graph illustrating source/drain dopant diffusion for aconventional Si channel during spike anneal at RMG.

FIG. 7 is a graph illustrating the PTS dopant diffusion for aconventional SiGe channel during spike anneal.

FIGS. 8-15 illustrate an exemplary fabrication process of forming asemiconductor device according to an embodiment, in which:

FIG. 8 is a cross-sectional view illustrating a portion of thesemiconductor device according to an embodiment including an SiGechannel and a dummy gate;

FIG. 9 is a cross-sectional view illustrating a portion of thesemiconductor device according to an embodiment including an Si channeland a dummy gate;

FIG. 10 is a cross-sectional view of a portion of the semiconductordevice illustrating formation of a source/drain in the SiGe channel;

FIG. 11 is a cross-sectional view of a portion of the semiconductordevice illustrating the formation of a source/drain in the Si channel;

FIG. 12 is a cross-sectional view of a portion of the semiconductordevice including the SiGe channel illustrating the deposition of an ILDlayer followed by removal of the dummy gate and dummy oxide;

FIG. 13 is a cross-sectional view of a portion of the semiconductordevice including the Si channel illustrating the deposition of an ILDlayer followed by removal of the dummy gate and dummy oxide;

FIG. 14 is a cross-sectional view of a portion of the semiconductordevice including the SiGe channel illustrating the deposition of ahigh-k dielectric layer, a metal gate, and a fill metal; and

FIG. 15 is a cross-sectional view of a portion of the semiconductordevice including the Si channel illustrating the deposition of a high-kdielectric layer, a metal gate, and a fill metal.

FIG. 16 is a graph of Ge 2p intensity versus binding energy for hightemperature anneal at dummy gate on SiGe25% pFET.

FIG. 17 is a graph of Si 2p intensity versus binding energy for hightemperature anneal at dummy gate on SiGe25% pFET.

FIG. 18 is a graph illustrating high-field mobility versus spike annealtemperature at dummy gate.

FIG. 19 is a graph illustrating Nit versus spike anneal temperature atdummy gate.

DETAILED DESCRIPTION

It is understood in advance that, although embodiments of the inventioninclude a detailed description of the formation of and resultingstructures for a specific type of FET, implementation of the teachingsrecited herein are not limited to a particular type of semiconductordevice or IC architecture. Rather embodiments of the present inventionare capable of being implemented in conjunction with any other typesemiconductor device or IC architecture, now known or later developed,as long as the semiconductor device incorporates the essential featuresdescribed herein.

Various embodiments of the present invention are described herein withreference to the related drawings. Alternative embodiments can bedevised without departing from the scope of this invention. It is notedthat various connections and positional relationships (e.g., over,below, adjacent, etc.) are set forth between elements in the followingdescription and in the drawings. These connections and/or positionalrelationships, unless specified otherwise, can be direct or indirect,and the present invention is not intended to be limiting in thisrespect. Accordingly, a coupling of entities can refer to either adirect or an indirect coupling, and a positional relationship betweenentities can be a direct or indirect positional relationship. As anexample of an indirect positional relationship, references in thepresent invention to forming layer “A” over layer “B” include situationsin which one or more intermediate layers (e.g., layer “C”) is betweenlayer “A” and layer “B” as long as the relevant characteristics andfunctionalities of layer “A” and layer “B” are not substantially changedby the intermediate layer(s). In the following invention “front-side”refers to the surface on which the integrated circuit devices are madeprior to flipping over the FET, and “back-side” refers to the surfacethat is to become the top surface after the device is turned over andbonded to a handling wafer.

In modern integrated circuits, such as microprocessors, storage devicesand the like, a very large number of circuit elements, especiallytransistors, are provided on a restricted chip area. Transistors come ina variety of shapes and forms, e.g., planar transistors, FinFETtransistors, nanowire devices, etc. The transistors are typically eitherNMOS (NFET) or PMOS (PFET) type devices wherein the “N” and “P”designation is based upon the type of dopants used to create thesource/drain regions of the devices. So-called CMOS (Complementary MetalOxide Semiconductor) technology or products refers to integrated circuitproducts that are manufactured using both NMOS and PMOS transistordevices. Irrespective of the physical configuration of the transistordevice, each device includes drain and source regions and a gateelectrode structure positioned above and between the source/drainregions. Upon application of an appropriate control voltage to the gateelectrode, a conductive channel region forms between the drain regionand the source region.

For many early device technology generations, the gate structures ofmost transistor elements (planar and FinFET devices) were formed from aplurality of silicon-based materials, such as a silicon dioxide and/orsilicon oxynitride gate insulation layer, in combination with apolysilicon gate electrode. However, as the channel length ofaggressively scaled transistor elements has become increasingly smaller,many newer generation devices employ gate structures that containalternative materials in an effort to avoid the short channel effectswhich can be associated with the use of traditional silicon-basedmaterials in reduced channel length transistors. For example, in someaggressively scaled transistor elements, which can have channel lengthson the order of approximately 10-32 nm or less, gate structures thatinclude a so-called high-k dielectric gate insulation layer (k-value ofapproximately 10 or greater) and one or more metal layers that functionas the gate electrode have been implemented. Such alternative gatestructures—typically known as high-k/metal gate structures (HK/MGstructures)—have been shown to provide significantly enhancedoperational characteristics over the heretofore more traditional silicondioxide/polysilicon gate structure configurations.

One well-known processing method that has been used for forming atransistor with a high-k/metal gate structure is the so-called “gatelast” or “replacement gate” technique. Generally, the replacement gateprocess involves: forming a basic transistor structure (planar, FinFET,nanowire, etc.) with a sacrificial or dummy gate structure positionedbetween sidewall spacers; forming the source/drain regions for thedevice; performing the necessary anneal process to activate implanteddopant materials; removing the sacrificial gate structure so as todefine a gate cavity for the replacement gate structure between thespacers; depositing a high-k gate insulation layer and a plurality ofmetal layers in the gate cavity; performing a CMP process to removeexcess materials positioned outside of the gate cavity; recessing thegate materials within the gate cavity to make room for a gate cap layer;and forming a gate cap layer in the gate cavity above the recessed gatematerials.

However, as the gate length of transistor devices has decreased, thephysical size of the gate cavity has also decreased. Thus, it isbecoming physically difficult to fit all of the layers of materialneeded for a high-k dielectric/metal gate (HK/MG) replacement gatestructure within such reduced-size gate cavities, particularly for NMOSdevices, due to the greater number of layers of material that aretypically used to form the HK/MG structures for the NMOS devices ascompared to PMOS devices. For example, as gate lengths continue todecrease, voids or seams can be formed as the various layers of materialare deposited into the gate cavity. That is, as the layers of materialfor the replacement gate are formed in the gate cavity, the remainingspace within the gate cavity becomes very small. As the later metallayers are formed, the remaining space within the gate cavity can beonly about 1-2 nm in width or even smaller. In some cases, there can beessentially no remaining space in the gate cavity. This can lead toso-called “pinch-off” of metal layers such that voids or seams can beformed in the overall replacement gate structure, which can result indevices that perform at levels less than anticipated or, in some cases,the formation of devices that are simply not acceptable and have to bediscarded.

Further, dangling bonds at the silicon/silicon oxide interface insemiconductor devices are believed to be the cause of observed non-idealcapacitance-voltage characteristics and reduced channel conductance. Lowtemperature post-metallization annealing in a hydrogen-containingatmosphere is typically used in the semiconductor device fabricationprocess, to passivate these dangling bonds. During operation, however,transistor performance can degrade, and this degradation has beencorrelated to the removal of hydrogen from the silicon/silicon oxideinterface, due to collisions between heated carriers and the interface.This degradation in hot carrier lifetime (also referred to as HCllifetime) is exacerbated by the ever ongoing miniaturization ofsemiconductor devices, and has become a significant limitation in thefurther shrinkage of semiconductor devices.

For example, a metal layer formed from a metal that can serve as abarrier layer to protect the high-k gate insulation layer can besubjected to a so-called “spike anneal at replacement metal gate (RMG)”process that will be performed to increase the reliability of the high-kgate insulation layer. In an example, a metal layer can be formed byperforming a plasma-enhanced physical vapor deposition (PVD) process. Asilicon-containing material layer, such as polysilicon or amorphoussilicon, can be blanket-deposited on the product so as to over-fill thegate cavity. The silicon-containing material layer can be formed byperforming, for example, a CVD process. After the silicon-containingmaterial layer is formed, an anneal process can be performed to increasethe reliability of the high-k gate insulation layer. The parameters ofsuch an anneal process are well known to those skilled in the art. Thesilicon-containing layer can then be removed by performing an etchingprocess. In some cases, metal layer that was used in the spike anneal ofthe high-k gate insulation layer can be removed (by selective etchingrelative to the high-k gate insulation layer) and a “new” metal layercan be formed on the high-k gate insulation layer.

In recent years, strain engineering has been used as a means to increasethe performance of semiconductor devices. Strain engineering introducesa strain into material within a channel region of a semiconductor deviceto improve the performance of the device. Strain is often induced byforming a lattice mismatch between materials in the channel region. Forexample, a lattice mismatch can be formed by depositing a layer ofsilicon over layer of silicon germanium. The atoms in the silicon layeralign with the atoms of the underlying silicon germanium layer (whichare arranged further apart), stretching the silicon material. Thestretched silicon material reduces interference with the movement ofcharge carriers, thereby improving mobility within the channel region.

A promising dual channel CMOS integration schemes for futuretechnologies is to use tensile-strained Si for nFETS andcompressively-strained SiGe grown on an Si substrate for pFETs. However,for replacement metal gate processes, high temperature spike anneal isnecessary to improve SiGe pFET performance while an Si nFET doesn'tnecessarily have to get processed. Further, the spike anneal at RMG alsoincreases equivalent oxide thickness of gate stack as spike annealtemperature increases. For example, FIG. 1 is a graph illustratingcapacitance equivalent thickness (CET) (CET=EOT+0.4 A) increases as thespike temperature increases. As shown in FIG. 2, an increase in spikeanneal temperature degrades Toxgl, wherein Toxgl stands for gatedielectric thickness for gate leakage calculation.

FIGS. 3-4 illustrate the impact of spike anneal at RMG on an SiGe gatestack. FIG. 4 illustrates the density of interface trap (D_(it))decreases as spike anneal temperature increases.

In addition, a spike anneal package at RMG is not suitable for nanosheetor aggressively scaled FinFET applications, which have a tight Finpitch. The spike package can pinch-off the space between each sheet orFin and therefore increase difficulty in removing the annealed Siresidue, as illustrated in Energy Dispersive X-Ray microanalysis of thenanosheet nFET of FIGS. 5A-5B. As shown in FIG. 5A, the SiGe layer isnot fully released. Further, the a-Si residue remains after spike annealas shown in the box of FIG. 5B. As shown in FIGS. 5A-5B, the a-Siresidue cannot be removed totally after spike anneal. Even under thebest conditions, it is challenging to remove a-Si for wide sheetapplications.

High thermal budget of spike package at RMG is another concern fordiffusion of the source/drain and punch-through stopper dopants into thechannel, which is critical to control short channel devices performance.FIGS. 6-7 illustrate source/drain dopant and PTS dopant diffusion,respectively, due to thermal budget. In FIG. 6, x-axis is the lateralposition of short channel device along the source to drain. Y-axis isthe doping concentration of device. Thus, initial channel length isdefined approximately 15 nm. In FIG. 7, x-axis is the vertical positionof device, where SiGe0.25 is the surface (channel) on Si substrate.Y-axis is the doping concentration of device. SiGe0.25 channel isundoped before spike anneal. As shown in FIG. 6, the source/drain dopant(P) diffuses into the Si channel during spike anneal. As shown in FIG.7, the PTS dopant (As) also diffuses into the SiGe channel during spikeanneal.

Embodiments of the present invention are directed to a spike annealprocess to improve the gate stack on a Si/SiGe dual channel CMOStransistor. An exemplary transistor includes a SiGeOx layer on an SiGechannel and the use of SiO₂ layer on an Si channel as a dummy oxide,followed by high temperature dummy gate anneal (950° C. to 1077° C.).The high temperature dummy gate anneal only modifies the SiGe surfacedue to the reaction of SiGiOx dummy oxide with SiGe surface during.After the high temperature dummy gate anneal, a Si-rich SiGe surface isformed, resulting in a low interface trap charge and high hole mobilityin SiGe pFET. For the Si nFET, there is no reaction of SiO₂ dummy oxidewith the Si surface during the dummy gate anneal.

The Si-rich SiGe surface is defined as the Ge content at the SiGesurface is at least 10% lower than SiGe channel layer. For example, ifthe Ge content at the SiGe surface is less than 15% on SiGe25% layerafter dummy gate anneal, we call it as Si-rich SiGe surface.

FIGS. 8-15 illustrate an exemplary fabrication process of forming asemiconductor device according to an embodiment.

As shown in FIG. 8, a first dummy gate 12 and first dummy oxide 14 isprovided between first spacers 16 on a SiGe channel 18. The first dummyoxide layer 14 includes SiGeOx. As shown in FIG. 8, a second dummy gate26, second dummy oxide 28, and second spacers 30 are formed on a Sichannel 32. Although Si is the predominately used semiconductor materialin wafer fabrication, other materials can be used including, but notlimited to, germanium, gallium arsenide, gallium nitride, cadmiumtelluride, and zinc selenide. The semiconductor channels can include Si,SiGe, SiGeC, Si:C, polysilicon, epitaxial Si, amorphous Si, andmulti-layers thereof. In an example, FIG. 8 refers to a pFET and FIG. 9refers to an nFET. As shown in both FIGS. 8-9, the respective channelscan include shallow trench isolation portions 24.

The dummy oxides 14, 28 and dummy gates 12, 26 can include a sacrificialpolysilicon material that can be deposited using a conventional chemicalvapor deposition (CVD) process and/or plasma enhanced CVD on therespective channels. As understood by those skilled in the art, thepolysilicon material (with the oxide) are associated with the formationof structures commonly referred to as “dummy gate” structures. Thepolysilicon material of the dummy gate structures will be subsequentlyremoved later in the fabrication process and replaced with a metal gatestack defining the actual operating gate electrode for the transistordevices (this process referred to in the art as a “replacement metalgate (RMG)” process). The top surface of the sacrificial polysiliconmaterial deposit can be polished using conventional chemical-mechanicalplanarization (CMP) techniques to provide a planar top surface betweenthe respective spacers.

The portions of the semiconductor illustrated in FIGS. 8-9 are annealed.The annealing conditions can be any suitable annealing conditions. Forexample, the portions illustrated in FIGS. 8-9 can be annealed in anitrogen-containing atmosphere. This atmosphere preferably contains80-100% nitrogen, by volume. The remaining portion of the atmosphere isnot limited, but preferably contains an inert gas, such as helium, neon,argon, krypton, xenon and mixtures thereof. Other possible gases includehydrogen (a small amount of which is commonly present in deuterium), andhydrocarbons or deuterated hydrocarbons such as methane and ethane.

The annealing temperature can be at least 800° C. The maximumtemperature for annealing is limited by the tolerance of the structurebeing annealed to heating without being damaged. In an example, theannealing temperature is between about 950 and 1080° C. The annealingtime can be from 1 sec to 10 sec.

The high temperature dummy gate anneal causes the reaction of SiGeOxwith SiGe channel (Ge+GeO₂→2GeO) that results in GeO desorption andprovides a Si— rich top surface 20 on SiGe channel 18 (as shown in FIG.10). During the high temperature anneal, no reaction occurs between theSiOx and the Si channel.

As shown in FIG. 10, after the high temperature anneal is performed, asource/drain 32 is formed in the SiGe channel and in the Si channel, asshown in FIG. 11. The formation of the source/drain can be by anysuitable method. S/D formation can be formed by ion implantation,epitaxial growth, and plasma doping. Si nFET S/D dopants can includephosphorus, arsenic, and combinations thereof. SiGe pFET S/D dopants caninclude boron, gallium, and combinations thereof.

As shown in FIGS. 12-13, a dielectric layer 34 can be deposited andplanarized on both the portion of the semiconductor device including aSiGe channel 18 and the Si channel 32. The method includes removal ofthe first dummy gate 12, thereby exposing the Si-rich top surface 20 ofthe SiGe channel, and removal of the second dummy gate 26 exposing asurface of the Si channel 32. The removal of the first dummy gate andsecond dummy gate can be simultaneous.

FIGS. 14-15 illustrate the deposition of a high-k dielectric layer 36,followed by the deposition of a metal gate layer 38, and the depositionof a fill metal 40. The high-k dielectric layer can be selected fromsilicon nitride, aluminum oxide, zirconium oxide, titanium oxide,tantalum pentoxide, barium-strontium-titanate, strontium-titanate-oxide,lead-zirconium-titanate, and combinations thereof. Dielectric materialshaving high dielectric constants are known as “high K” materials. Awidely used dielectric material is silicon dioxide (SiO₂), which has adielectric constant of approximately 3.9. SiO₂ has been used as thedielectric material for conventional capacitors and transistors. As usedherein, high-k dielectric materials have a dielectric constant greaterthan SiO₂.

In an example, the metal gate layer 38 can include TiN, TiAl, TaN, andcombinations thereof. The high-k dielectric layer 36 can include HfO₂,Al₂O₃, La₂O₃, Y₂O₃, ZrO₂, and combinations thereof. For example, thehigh-k dielectric layer 36 can include HfAlOx, HfYOx, HfYOx, andcombinations thereof. In an example, the fill metal 40 can be tungsten,copper, titanium, and combinations thereof. As shown in FIGS. 14-15, anozone layer can be formed between the top surface of the SiGe and Sichannels and the high-k dielectric layer 36. The ozone layer 42 can beapplied by subjecting the gate stack to ozone and water for ten secondsbefore applying the high-k dielectric layer 36.

EXAMPLES

For the examples in FIGS. 16-17, a high temperature spike anneal wasperformed above 1000° C. A SiGeOx/SiGe layer/Si substrate is used forFIGS. 16-17, where the thickness of SiGeOx is in the range of 1 to 4 nmand the thickness of SiGe layer is 5 to 50 nm.

FIG. 16 is a graph of Ge 2p intensity versus binding energy for hightemperature dummy gate anneal on SiGe25% pFET. FIG. 17 is a graph of Si2p intensity versus binding energy for high temperature dummy gateanneal on SiGe25% pFET. As illustrated in FIGS. 16-17, high temperaturedummy gate anneal provides a Si-rich top surface in SiGe channel due tothe reaction of SiGeOx dummy oxide with the SiGe surface. The intensityof XPS is proportional to Si/Ge percentage in the SiGe layer. After hightemperature dummy gate anneal at 1044° C., a dramatic reduction ofintensity in the portion of the Ge 2p core-level spectra associated withGe—Ge element is observed, while Si 2p core-level spectra shows theincrease of Si—Si element intensity. FIGS. 16-17 indicate a Si-rich topsurface in the SiGe channel is formed.

For FIGS. 18-19, the dielectric layer is HfO₂ and gate material isTiN/TiAlC/TiN clustered layer, and fill metal is tungsten. FIG. 18illustrates high-field mobility versus dummy gate anneal temperature.FIG. 19 illustrates number of interface trap versus dummy gate annealtemperature.

FIGS. 18-19 relate to an example of a SiGe25% pFET manufacturedaccording to three different methods. Split 1 refers to a pFETmanufactured with a method that skips the spike anneal at RMG, Split 2refers to a pFET manufactured using conventional methods. SiGeOx/SiGelayer/Si substrate is used for FIGS. 16-17, where the thickness ofSiGeOx is in the range of 1 to 4 nm and the thickness of SiGe layer is 5to 50 nm. Split 3 refers to the disclosed method including a hightemperature dummy gate anneal including a 1044° C. anneal temperaturespike.

The disclosed method significantly reduces the thermal budget of thedownstream process, especially for RMG process, as compared toconventional processes.

Deposition is any process that grows, coats, or otherwise transfers amaterial onto the wafer. Available technologies include, but are notlimited to, thermal oxidation, physical vapor deposition (PVD), chemicalvapor deposition (CVD), electrochemical deposition (ECD), molecular beamepitaxy (MBE) and more recently, atomic layer deposition (ALD) amongothers.

For the sake of brevity, conventional techniques related tosemiconductor device and IC fabrication cannot be described in detailherein. Moreover, the various tasks and process steps described hereincan be incorporated into a more comprehensive procedure or processhaving additional steps or functionality not described in detail herein.In particular, various steps in the manufacture of semiconductor devicesand semiconductor-based ICs are well known and so, in the interest ofbrevity, many conventional steps have only been mentioned briefly hereinor have omitted entirely without providing the well-known processdetails.

By way of background, however, a more general description of thesemiconductor device fabrication processes that can be utilized inimplementing one or more embodiments of the present invention will nowbe provided. Although specific fabrication operations used inimplementing one or more embodiments of the present invention can beindividually known, the disclosed combination of operations and/orresulting structures of the present invention are unique. Thus, theunique combination of the operations described in connection with thepresent embodiments of the invention utilize a variety of individuallyknown physical and chemical processes performed on a semiconductor(e.g., silicon) substrate, some of which are described in the followingimmediately following paragraphs.

In general, the various processes used to form a micro-chip that will bepackaged into an IC fall into four general categories, namely, filmdeposition, removal/etching, semiconductor doping andpatterning/lithography. Deposition is any process that grows, coats, orotherwise transfers a material onto the wafer. Available technologiesinclude physical vapor deposition (PVD), chemical vapor deposition(CVD), electrochemical deposition (ECD), molecular beam epitaxy (MBE)and more recently, atomic layer deposition (ALD) among others.Removal/etching is any process that removes material from the wafer.Examples include etch processes (either wet or dry), andchemical-mechanical planarization (CMP), and the like. Semiconductordoping is the modification of electrical properties by doping, forexample, transistor sources and drains, generally by diffusion and/or byion implantation. These doping processes are followed by furnaceannealing or by rapid thermal annealing (RTA). Annealing serves toactivate the implanted dopants. Films of both conductors (e.g.,poly-silicon, aluminum, copper, etc.) and insulators (e.g., variousforms of silicon dioxide, silicon nitride, etc.) are used to connect andisolate transistors and their components. Selective doping of variousregions of the semiconductor substrate allows the conductivity of thesubstrate to be changed with the application of voltage. By creatingstructures of these various components, millions of transistors can bebuilt and wired together to form the complex circuitry of a modernmicroelectronic device.

Fundamental to the above-described fabrication processes issemiconductor lithography, i.e., the formation of three-dimensionalrelief images or patterns on the semiconductor substrate for subsequenttransfer of the pattern to the substrate. In semiconductor lithography,the patterns are a light sensitive polymer called a photo-resist. Tobuild the complex structures that make up a transistor and the manywires that connect the millions of transistors of a circuit, lithographyand etch pattern transfer steps are repeated multiple times. Eachpattern being printed on the wafer is aligned to the previously formedpatterns and slowly the conductors, insulators and selectively dopedregions are built up to form the final device.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A method of fabricating a semiconductor device,the method comprising: forming at least one of a first semiconductorregion and a second semiconductor region different from the firstsemiconductor region, wherein forming at least one of the firstsemiconductor region and second semiconductor region comprises: forminga first semiconductor channel comprising a first semiconductor material;forming a first set of spacers extending from the top surface of thesemiconductor channel so as to define a first gate between the first setof spacers; and forming a semiconductor-rich surface on a portion of thetop surface of the semiconductor channel between the first set ofspacers, wherein the first gate includes a first high-k dielectric layerin contact with the spacers, and a first metal gate material in contactwith the high-k dielectric layer.
 2. The method of claim 1, whereinforming the first semiconductor region includes forming a p-field effecttransistor (pFET) region, and wherein forming the pFET region furthercomprises: forming a SiGe channel that defines the first semiconductorchannel; and forming a Si-rich region on a portion of the top surface ofthe SiGe channel that defines the semiconductor-rich surface, andwherein forming the second semiconductor region includes forming ann-field effect transistor (nFET) region, wherein forming the n-fieldeffect transistor (nFET) region further comprises: forming a Si channel;and forming a second set of spacers extending from the top surface ofthe Si channel so as to define a second gate between the second set ofspacers, wherein the second gate includes a second high-k dielectriclayer in contact with the second set of spacers, and a second metal gatematerial in contact with the second high-k dielectric layer.
 3. Themethod of claim 2 further comprising forming a first high-k dielectriclayer in contact with the first set of spacers.
 4. The method of claim 3further comprising forming a second high-k dielectric layer in contactwith the second set of spacers.
 5. The method of claim 3 furthercomprising forming a first ozone layer on the Si-rich layer.
 6. Thesemiconductor device of claim 5, further comprising forming the firstozone layer between the Si-rich layer and the first high-k dielectriclayer.
 7. The method of claim 6 further comprising forming a secondozone layer on the Si channel between the second set of spacers.
 8. Themethod of claim 7, further comprising forming the second ozone layerbetween the Si channel between the second high-k dielectric layer. 9.The method of claim 2, further comprising forming source and drainregions within the n-field effect transistor (nFET) region and thep-field effect transistor (pFET) region.
 10. The method of claim 4,wherein the first high-k dielectric layer and second high-k dielectriclayer are independently selected from silicon nitride, aluminum oxide,zirconium oxide, titanium oxide, tantalum pentoxide,barium-strontium-titanate, strontium-titanate-oxide,lead-zirconium-titanate, and combinations thereof.
 11. The method ofclaim 2, wherein the first gate material and second gate material areindependently selected from TiN, TiAl, TaN, and combinations thereof.12. The method of claim 2, wherein the Si-rich layer has a concentrationof Ge that is at least 10% lower than the concentration of Ge in theSiGe channel.
 13. The method of claim 2, wherein the Si-rich layer has aconcentration of Ge that is at least 5% lower than the concentration ofGe in the SiGe channel.
 14. A method of fabricating a semiconductordevice comprising: forming at least one of a first semiconductor regionand a second semiconductor region different from the first semiconductorregion, the first semiconductor region including a first semiconductorchannel having a semiconductor-rich upper surface, while the secondsemiconductor region includes a second semiconductor channel excludingthe semiconductor-rich upper surface, wherein forming the firstsemiconductor region further comprises: forming a first set of spacersextending from the top surface of the first semiconductor channel so asto define a first gate between the first set of spacers, the first gateincluding a first high-k dielectric layer in contact with the spacers,and a first metal gate material in contact with the high-k dielectriclayer.
 15. The method of claim 14, wherein forming the firstsemiconductor region includes forming is a p-field effect transistor(pFET) region, wherein forming the pFET region further comprises:forming SiGe material that defines the first semiconductor channel; andforming a Si-rich region on a portion of the top surface of the SiGematerial to define the semiconductor-rich surface.
 16. The method ofclaim 15, wherein forming the second semiconductor region includesforming an n-field effect transistor (nFET) region, wherein forming thenFET region further comprises: forming Si material that defines thesecond semiconductor channel; and forming a second set of spacersextending from the top surface of the Si material so as to define asecond gate between the second set of spacers, and wherein the secondgate includes a second high-k dielectric layer in contact with thesecond set of spacers, and a second metal gate material in contact withthe second high-k dielectric layer.
 17. The method of claim 16 furthercomprising forming an ozone layer on the Si-rich layer.
 18. The methodof claim 17, further comprising forming the ozone layer between theSi-rich layer and the first high-k dielectric layer.
 19. The method ofclaim 18 further comprising forming an ozone layer on the Si channelbetween the second set of spacers.
 20. The method of claim 19, furthercomprising forming the ozone layer between the Si channel and the secondhigh-k dielectric layer.